JPH10268362A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the display device which is small in power consumption and reducible in power capacity and can operate for a long time at the time of portable use. SOLUTION: A matrix type display device featuring a ferroelectric layer 26 of 10 to 5000 in dielectric constant which is arranged in contact with a pixel electrode 18 arranged facing one surface of a liquid crystal layer 50, a counter electrode 45 which is set opposite the pixel electrode across the liquid crystal layer and arranged facing the liquid crystal layer, and meshed column electrodes 27 and meshed row electrodes 28 which are arranged between the liquid crystal layer and ferroelectric layer has the column electrodes and row electrodes applied with a voltage enabling the polarization inversion of the ferroelectric layer, so that the ferroelectric layer holds image information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display including a dielectric layer and capable of reducing power consumption.

[0002]

2. Description of the Related Art A liquid crystal display device for displaying an image by a pixel matrix defined by a matrix of pixels has a transmission mode in which light is transmitted from a back surface of a display surface by a backlight for display and a method for reducing power consumption. It is driven by any of the reflection modes in which the backlight is eliminated and the display on the display surface can be recognized only by the reflection of ambient light.

In the transmission mode described above, the backlight occupies about half of the power consumption of the entire display device. Therefore, driving the display device in the reflection mode is very useful for reducing power consumption.

In recent years, with the expansion of demand for long-term use in word processors, laptop personal computers, small game machines, portable telephones, electronic organizers, portable electronic books, and the like, liquid crystal display devices in the reflection mode have also been used. Therefore, further reduction in power consumption is desired.

In a liquid crystal display device, the power consumption can be reduced by reducing each of the capacity, drive frequency and drive voltage of the display device.
It is beneficial to lower the drive voltage because it affects the order of the power. Note that the capacitance of the display device is determined by the wiring structure and the dielectric material sandwiched between the wirings. The driving frequency is determined depending on the cycle of rewriting the screen being displayed. For example, a 640 × 480 pixel VGA
(Video graphics array)
This is a frequency at which a cycle of / 60 seconds can be rewritten.

As a method for reducing the power consumption of a liquid crystal display device, for example, Japanese Patent Application No. 279706 proposes a driving method for lowering the driving frequency without rewriting a still image. In addition, for example, Japanese Patent Application No. 5-45230 proposes a method of reducing power consumption by shifting a power supply voltage.

In addition to the above-described method of lowering the drive frequency and shifting the drive voltage, for example,
In Japanese Patent Application Laid-Open No. 196,582 or JP-A-3-77922, a memory is arranged for each pixel, and for a still image, a display signal is transmitted to each pixel, and then a signal held in the memory of the pixel is used. Is always displayed.

[0008]

In the above example in which the memory is arranged for each pixel, the power consumption of a still image is
Since the power is reduced to only the power required for the polarity inversion, the power consumption theoretically approaches “0” without limit.

However, when displaying a moving image, the above-mentioned memory needs to be rewritten at high frequency, and it is necessary to reduce the power consumption by writing to the memory. There is a problem that cannot be fully utilized. An object of the present invention is to provide a display device that consumes less power, can reduce power supply capacity, and can operate for a long time when it is carried.

[0010]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problems, and is arranged in contact with a first electrode which is arranged on one surface of a liquid crystal layer, and has a dielectric constant. 1
A ferroelectric layer of 0 or more and less than 5,000, a second electrode facing the first electrode with the liquid crystal layer interposed, and a second electrode arranged facing the liquid crystal layer; And a third electrode disposed between the ferroelectric layer and the ferroelectric layer.

The third electrode of the liquid crystal display device according to the present invention has a first direction and a second direction substantially orthogonal to the first direction.
Characterized in that it is a mesh-like electrode including a plurality of electrodes each extending in the direction of.

Further, the third electrode of the liquid crystal display device of the present invention is arranged so as to divide an area corresponding to one pixel of the liquid crystal layer divided by the first electrode into a plurality of independently drivable areas. It is characterized by being.

Still further, the liquid crystal display device of the present invention comprises:
A semiconductor layer is provided between the ferroelectric layer and the third electrode. Still further, the first electrode of the liquid crystal display device according to the present invention is characterized in that the first electrode is a reflective electrode that defines a region corresponding to one pixel of the liquid crystal layer.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing a section of a first embodiment of the active matrix type liquid crystal display device of the present invention.

As shown in FIG. 1, an active matrix type liquid crystal display device (hereinafter, simply referred to as a liquid crystal display device) 1 is a first type in which a plurality of thin film transistors (hereinafter, referred to as TFTs) are arranged in a matrix. It comprises a substrate, ie, an array substrate 10, a counter substrate 40 substantially parallel to the array substrate at a predetermined distance from the array substrate, and a liquid crystal composition 50 interposed between the counter substrate 40 and the array substrate 10. .

The array substrate 10 includes an insulating substrate (support glass) 11 made of a transparent material such as glass, and various materials and pixels constituting TFT elements provided in the following process on one surface. The undercoat layer 12 also serves as a surface treatment to prevent a chemical reaction between the electrode material and the like and the insulating substrate 11 and to provide a uniform supply of the electrode material and the transistor material to the insulating substrate 11.

On the undercoat layer 12, a first metal or semiconductor for providing a scanning line (row selection line) corresponding to the gate electrode of the TFT and formed integrally with the gate electrode is provided. An electrode portion 13 is formed. The scanning line 13 is a single layer or a multilayer of a metal material such as Al (aluminum), Ti (titanium), Cr (chromium), Mo (molybdenum), Ta (tantalum) or W (tungsten), or an alloy thereof. Provided by Also, a predetermined position of the undercoat layer 12 (generally, near the center of a pixel electrode described later).
Is provided with a storage capacitor electrode (not shown).

Above the scanning line 13 and the storage capacitor electrode, that is, on the side facing the liquid crystal composition 50 when the array substrate 10 is assembled with the counter substrate 40, the scanning line 13 and the storage capacitor electrode are made of, for example, silicon nitride. An insulating layer, that is, a gate insulating film 14 is formed to cover each of them.

An a-Si (amorphous silicon layer or amorphous silicon) layer 15 as a semiconductor layer and an inorganic protective film are provided above the gate insulating film 14 and at least in a portion corresponding to the gate electrode of the scanning line 13. 16 are sequentially stacked. In addition, as the inorganic protective film 16, for example,
SiNx (silicon nitride) or the like is used. Each of the gate insulating film 14, the a-Si layer 15, and the inorganic protective film 16 has a thickness of 400 nm, for example, by a plasma CVD method, a normal pressure CVD method, a low pressure CVD method, or the like.
m, 50 nm and 200 nm.

On the inorganic protective film 16 and the a-Si layer 15, a low-resistance semiconductor layer, that is, an ohmic contact layer 17 is disposed so as to cover the entire area of the a-Si layer 15 and a part of the inorganic protective film 16. ing. As the ohmic contact layer 17, for example, amorphous silicon doped with phosphorus is used.

The region where the scanning line (gate electrode) 13 is formed, the ohmic contact layer 17 and the a-Si layer 1
A transparent conductive film used as a pixel electrode, that is, IT
An O film 18 is formed. The ITO film 18 is formed, for example, by a plasma CVD method, a normal pressure CVD method, or a low pressure C method.
The undercoat layer 12 has a predetermined thickness by a VD method or the like.
After being deposited thereon, it is formed in a predetermined shape and a predetermined area by dry etching (not described in detail) or the like.

At a predetermined position on the undercoat layer 12 in a direction orthogonal to the gate electrode (scanning line) 13, substantially the same metal or semiconductor as the scanning line (gate electrode) 13 or any combination thereof is used. Are formed, ie, a signal line (column selection line) 19 made of a material given with. The signal line 19 is insulated from the pixel electrode 18 by being covered with a passivation film (insulating film) 20, and is formed integrally with a drain electrode of a TFT described below.

The region covering a part of the ohmic contact layer 17 and the pixel electrode 18 is a single layer or a laminated layer made of a metal or an alloy and is used as a source electrode and a drain electrode of a TFT. 17 are integrally formed on the gate insulating film 16 by dry etching or the like.
Electrode portions 21 and 22 divided into two regions are formed. The electrode portion 21 is used as a source electrode, and the electrode portion 22 is used as a drain electrode. In this way, a TFT 23 in which the scanning line 13 is used as a gate electrode and the drain electrode 22 is connected to the signal line 19 is formed for each of the plurality of regions divided into a matrix by the scanning line 13 and the signal line 19.

The electrode portions 21 and 22 are protected by a passivation film 24. In addition, an interlayer insulating film 25 is formed to a predetermined thickness in substantially the entire area of the pixel electrode 18 and the entire area of the passivation film 24, that is, the entire area on the surface layer side of the insulating substrate 11.

In a region covering substantially the entire area of the pixel electrode 18 with the interlayer insulating film 25 interposed, a dielectric constant of 10 to 50
At 00, a ferroelectric layer 26 having a thickness of approximately 0.5 to 1000 μm is formed. Note that the ferroelectric layer 2
6 is a mesh-like electrode and a pixel electrode 18 described below.
, It is possible to be exposed to a large electric field, an image is written by the TFT 23,
Further, regarding the pixel in which the electric field is applied to the mesh electrode,
Functions as an image memory. As a material suitable for the ferroelectric layer 26, BaTiO ₃ (barium titanate:
Perovskite oxide), PZT (Pb (Zr, T
i) O ₃ ), Bi ₄ Ti ₃ O ₁₂ (bismuth titanate: layered oxide), organic materials such as vinylidenefluoride (VDF), and trifluoroethylene (TrFE) can be used. is there.

On the ferroelectric layer 26, an area corresponding to one pixel divided by the scanning lines 13 and the signal lines 19 is divided into a plurality of strip-shaped areas, and is formed in a mesh shape extending in a first direction. A column electrode (hereinafter, referred to as a Y-direction electrode) 27, a mesh-shaped row electrode (hereinafter, referred to as an X-direction electrode) 28 extending in a second direction orthogonal to the Y-direction electrode 27, and Y-direction electrodes 27 and X At the position where the direction electrodes 28 intersect, an interlayer insulating spacer 29 for maintaining the insulating distance between the two electrodes and insulating them is arranged. In addition, as shown in FIG. 2, the interlayer insulating spacer 29 has two electrodes 27 and 28 in plan view.
Are arranged only in the area near the intersection of. The Y-direction electrode 27 and the X-direction electrode 28 are connected to the scanning line 13 and the signal line 1
One pixel divided by 9 is further subdivided.

The Y-direction electrode 27, the X-direction electrode 28 and the TFT 2 located on the ferroelectric layer 26 of the array substrate 10
All of 3 are further covered by the orientation film 30 together with the interlayer insulating film 25. The remaining surface of the insulating substrate 11, that is, the surface facing outward when the array substrate 10 and the opposing substrate 40 are assembled, protects the surface of the insulating substrate 11 and the wavefront of light passing through the insulating substrate 11. Is provided integrally with the insulating substrate 11 for matching the above characteristics.

Like the array substrate 11, the opposing substrate 40 includes an insulating substrate (support glass) 41 formed of a transparent material such as glass, the array substrate 10 and the opposing substrate 4
0 is located on a surface facing outward when assembled, and includes a polarizing plate 42 for protecting the surface of the insulating substrate 41 and matching the characteristics of the wavefront of light passing through the insulating substrate 41.

On the remaining surface of the insulating substrate 41, when the array substrate 10 and the opposing substrate 40 are overlapped, the insulating substrate 4 is located at a position facing the TFT 23 on the array substrate 10 side.
In order to prevent the TFT 23 from erroneously operating due to the light passing through 1, a light-shielding film 43 that shields the TFT 23 and light traveling in the vicinity thereof is formed. The size of the light-shielding film 43 is such that the shadow of the light-shielding film 43 is projected even when the center of the light-shielding film 43 and the center of the TFT 23 are displaced due to an error when the array substrate 10 and the counter substrate 40 are overlapped. The size is determined so that the TFT 23 does not come off from the region.

On the side of the surface layer of the light shielding film 43 (the surface facing the liquid crystal composition 50 when the counter substrate 40 and the array substrate 10 are assembled), R (red), G (green), and B (blue) A colored resin layer colored with a dye corresponding to each of the color filters, that is, a color filter 44 is disposed. On the surface layer (the surface facing the liquid crystal composition 50 when the counter substrate 40 and the array substrate 10 are assembled) of the color filter 44,
A transparent conductive film used as a counter electrode, that is, an ITO film 45 is disposed. In addition, an alignment film 46 on the counter substrate 40 side is formed on the entire surface layer of the counter electrode 45 (the surface facing the liquid crystal composition 50 when the counter substrate 40 and the array substrate 10 are assembled).

Next, the array substrate 10 and the opposing substrate 40 are opposed at a predetermined interval with a spacer (not shown) therebetween, and a liquid crystal material (liquid crystal composition) is injected between the substrates to form a liquid crystal layer 50. .

Hereinafter, the array substrate 10 and the counter substrate 40
The tape carrier package (TC
The liquid crystal display device 1 is formed by mounting a drive circuit (not shown) by the P) method and connecting a power supply device (not shown). The driving circuit includes a first driving circuit for driving the TFT 23, a Y-direction electrode 27 and an X-direction electrode 28.
Then, a second drive circuit for selectively applying a predetermined electric field is prepared.

Next, the operation of the liquid crystal display device 1 shown in FIG. 1 will be described. By applying a desired potential difference (electric field) between the pixel electrode 18 connected to one TFT 23 and the mesh electrodes 27 and 28 or between the mesh electrodes 27 and 28 and the counter electrode 45, the pixel electrode 18 As the pixel information is written into the ferroelectric layer 26 in the area, the liquid crystal layer is changed from transmission to absorption or from absorption to transmission.

Here, at the time of writing to the ferroelectric layer 26, between the pixel electrode 18 and the mesh electrodes 27 and 28, the dielectric used for the ferroelectric layer 26 has a coercive electric field equal to or higher than the coercive electric field at which the polarization is inverted. It is necessary to apply an electric field. When the image information is held by the ferroelectric layer 26, the pixel information (polarized charge) stored in the ferroelectric layer 26 is in direct contact with the liquid crystal layer 50 via the ferroelectric layer 26. Thus, an image is written on the liquid crystal layer 50.

More specifically, the ferroelectric layer 26 is formed as shown in FIG.
By applying the drive voltage having the waveform shown in FIG.
The operation on the electric field versus electric flux density (ED) hysteresis shown in FIG.

More specifically, assuming that a time for writing a positive signal when writing a signal to a pixel of interest at a certain timing during a screen rewriting period is Tw +, VG- is applied as a voltage of the signal line 19. The polarization direction of the ferroelectric layer 26 is saturated in the negative direction. That is, the direction of polarization is aligned in the negative direction (point a in FIG. 3B).

Subsequently, a voltage of Vw + corresponding to a video signal is applied (point b in FIG. 3 (b)), and then a reference potential Vz is applied (point c in FIG. 3 (b)). The voltage writing cycle (period) ends.

When the write cycle (period) ends,
The TFT 23 is turned off, and the electrode potential of the ferroelectric layer 26 is maintained at the reference voltage Vz. In this case, the polarization state of the ferroelectric of the target pixel is
In addition, the potential generated by the fixed charges generated by the polarization can be maintained. Note that by using a guest-host type liquid crystal material and a reflective type, it is not necessary to change the voltage of a signal line until rewriting is necessary, and the liquid crystal can be driven with low power consumption.

According to the driving method shown in FIG. 3, the screen rewriting period is completed, and during a period in which the screen rewriting is not required at all (non-change holding period), the gate potential is raised and the signal line 19 is changed. By applying the reference potential Vz to the pixel and writing the pixel, the drift of the potential of the pixel electrode 18 due to a leak current or the like can be reduced, and the fluctuation of the electric field applied to the liquid crystal layer can be suppressed.

On the other hand, when the cursor is blinked, when the display point is moved by the mouse or the pointer, or when only a part of the screen is rewritten,
By selectively increasing the voltage of the gate line 13 only for the pixel to be rewritten, a signal can be easily written.

In the driving method shown in FIG. 3, the TFT 23 is continuously turned on during the non-change holding period.
The reference voltage Vz may be intermittently written. This method is useful for reducing power consumption in the case where a DC voltage is applied to cause a resistance loss in a peripheral driving circuit.

In the example shown in FIG. 3, the polarization inversion, writing, and application of the reference voltage are performed on the ferroelectric layer 26 during the same period of selecting the pixel. The polarization saturation inversion, the writing, and the writing and the application of the reference voltage may be divided. In this case, the polarization saturation inversion may be performed for all pixels at the same time, and thereafter, the predetermined voltage Vw + may be written for each pixel.

In the equivalent circuit of the liquid crystal, when the time constant represented by the leak resistance connected in parallel to the liquid crystal detector is sufficiently large, the liquid crystal can be driven only by writing. On the other hand, if the display period has a length that cannot be ignored with respect to the time constant, the polarity of the voltage applied to the liquid crystal may be changed at any appropriate timing of a constant period or an irregular period.

Points (d), (e) and (d) in FIG. 3 (b) indicate the change in the polarity of the above-mentioned voltage, and the polarization is aligned in the positive direction at the voltage VR + (point (d) in FIG. 3 (b)). Vw- is applied (point e in FIG. 3B), and the reference voltage Vz is written (point f in FIG. 3B). In this case, FIG.
(B) If the repetition of the points d to f and the points a to c in FIG. 3B is provided by, for example, an AC voltage having a period approximately 1/10 of the time constant of the liquid crystal, the voltage is reduced by 5%. Since the voltage polarity is inverted, the rate of change in luminance at the time of inversion is substantially the same, and the change in luminance is visible but is within an acceptable range. Also, at the time of driving for inverting the voltage polarity, the structure of the liquid crystal display device shown in FIG.
Even if the number of pixels increases, the voltage applied to the dielectric and the liquid crystal can be accurately controlled, so that the absolute values of the positive and negative voltages can be made equal, and a DC voltage is applied to the liquid crystal, causing the image to burn. Good display can be obtained for a long period without any problem. It is also effective to store the positive and negative voltage application times in the system by an appropriate method, and to drive the system so that long-term positive / negative balance can be obtained.

FIG. 4 shows the potential distribution of the liquid crystal layer when the Y-direction electrode 27 and the X-direction electrode 28 are applied using the model of the liquid crystal display device shown in FIG. As shown in FIG. 4, the potential of the liquid crystal layer is
It can be seen that the potential of the mesh electrode at the intersection of the mesh electrode and the X-direction electrode 28 has risen to the potential of the mesh electrode.

From this fact, by selecting a material that switches the liquid crystal material at the above-mentioned potential, the information stored in the ferroelectric layer (dielectric) can be maintained even after the voltage application to the mesh electrode is stopped. It can be seen that the switching of the liquid crystal becomes possible by the (polarization charge amount). Also. By positively utilizing the potential distribution formed between the respective electrodes of the mesh electrode shown in FIG. 4, the inside of the pixel driven by one TFT 23 can be arbitrarily determined for each region divided by the mesh electrode. And the transmission and absorption can be controlled, and a plurality of gradations can be displayed. That is, as shown in FIG.
By providing many mesh electrodes in the pixel,
By forming a region where liquid crystal is switched (a hatched region in FIG. 5) and a region where the liquid crystal is not switched (a non-hatched region in FIG. 5), a halftone based on the area gradation is displayed for each display pixel. Enable. Note that FIG.
Is limited to a predetermined distance from the Y-direction electrode 27 and the X-direction electrode 28, as shown in the potential distribution of the liquid crystal layer shown in FIG. This is because the potential of the ferroelectric layer 26 decreases as the value increases, and the polarization of the dielectric does not occur.

FIG. 6 is a schematic sectional view showing another embodiment of the active matrix type liquid crystal display device described with reference to FIGS. In addition, about the structure same as the structure shown in FIG. 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

Referring to FIG. 6, the liquid crystal display device 100
Is an array substrate 110 on which a plurality of TFTs 23 are arranged in a matrix, a counter substrate 40 facing the array substrate 110 at a predetermined interval, and a liquid crystal composition interposed between the array substrate 110 and the counter substrate 40. Object 50

On the undercoat layer 12 provided on the insulating substrate 11 of the array substrate 110, a scanning line (row selection line) 13 also serving as a gate line and a storage capacitor electrode (not shown) are arranged, and a gate insulating film 14 is formed. Is formed.

The a-Si layer 1 is provided at least above the gate insulating film 14 at a portion corresponding to the gate electrode of the scanning line 13.
5 and an inorganic protective film 16 are sequentially laminated. a-S
An ohmic contact layer 17 is disposed over the entire area of the i-layer 15 and a part of the inorganic protective film 16, and at a position separated by a predetermined distance from a region where the ohmic contact layer 17 and the a-Si layer 15 are stacked. In addition, a transparent conductive film, that is, an ITO film 18 as a pixel electrode is formed.

A signal line (column selection line) 19 is formed at a predetermined position on the undercoat layer 12 in a direction orthogonal to the gate electrode (scanning line) 13. The signal line 1
9 is insulated from the ITO film (pixel electrode) 18 by being covered with a passivation film (insulating film) 20 and is formed integrally with a drain electrode of the TFT described below. On the ohmic contact layer 17, T
An electrode portion corresponding to the source electrode 21 of the FT and an electrode portion used as the drain electrode 22 are formed.
In this manner, for each of the plurality of regions divided into a matrix by the scanning line 13 and the signal line 19, the scanning line 13 is used as a gate electrode and the drain electrode 22 is used as a signal line 1
The TFT 23 connected to the TFT 9 is formed.

The electrode portions 21 and 22 are protected by the passivation film 24. In addition, an interlayer insulating film 25 is formed to a predetermined thickness in substantially the entire area of the pixel electrode 18 and the entire area of the passivation film 24, that is, the entire area on the surface layer side of the insulating substrate 11.

In a region covering the whole area of the pixel electrode 18 with the interlayer insulating film 25 interposed, the dielectric constant is 10 to 50.
At 00, a ferroelectric layer 26 having a thickness of approximately 0.5 to 1000 μm is formed.

Immediately above the ferroelectric layer 26, for example, a-
Si, GaAs, InN, AlN, BN, Se, Te,
Semiconductor layer 12 made of a semiconductor such as PbS or Bi ₂ Te ₃
6 are formed.

On the semiconductor layer 126, a mesh-like column electrode extending in a first direction that divides a region corresponding to one pixel divided by the scanning lines 13 and the signal lines 19 into a plurality of band-like regions. That is, the Y-direction electrode 27, a mesh-shaped row electrode extending in the second direction orthogonal to the Y-direction electrode 27, that is, the X-direction electrode 28, and the position where the Y-direction electrode 27 and the X-direction electrode 28 intersect each other, An interlayer insulating spacer 29 for maintaining the insulation distance and insulating.

Subsequently, a Y-direction electrode 27 and an X-direction electrode 28
All of the TFTs 23 are further covered with the interlayer insulating film 25 and the alignment film 30, and a polarizing plate 31 is provided on a surface facing outward when assembled with the counter substrate 40.

Hereinafter, a liquid crystal material (liquid crystal composition) is injected between the substrates by interposing a spacer (not shown) between the substrates at predetermined intervals, and a liquid crystal layer 50 is formed.
Next, the operation of the liquid crystal display device 100 shown in FIG. 6 will be described.

In the liquid crystal display device 100 shown in FIG. 6, basically, similarly to the liquid crystal display device 1 shown in FIG. 1 to FIG. And the X-direction electrode 28 in the second drive circuit,
By independently controlling each of them, a desired potential difference (electric field) is applied between the pixel electrode 18 connected to one TFT 23 and the mesh electrodes 27 and 28 or between the mesh electrodes 27 and 28 and the counter electrode 45. Pixel information is written into the ferroelectric layer 26 in a region corresponding to the pixel electrode 18, and the liquid crystal layer is changed from transmission to absorption or from absorption to transmission.

When writing to the ferroelectric layer 26,
Between the pixel electrode 18 and the mesh electrodes 27 and 28,
It is necessary to apply an electric field (potential difference) higher than the coercive electric field at which the ferroelectric layer 26 inverts the polarization.

Here, as shown in FIG. 4, when the potential distribution is obtained by using the model of the liquid crystal display device 100, the intersection position of the mesh-shaped electrode composed of the Y-direction electrode 27 and the X-direction electrode 28 and the Y-direction electrode 27 and the X-direction electrode 28, in almost the entire area,
It is recognized that the potential of the mesh electrode has been raised. That is, as is clear from FIG. 7, it is recognized that the electric potential of the liquid crystal layer becomes substantially uniform by sandwiching the semiconductor layer between the ferroelectric layer 26 and the mesh electrode.

Further, this is because, as shown in FIG. 8, by providing a large number of mesh-shaped electrodes in one pixel, the liquid crystal is not switched to the area where the liquid crystal is switched (the area hatched in FIG. 8). By forming an area (non-hatched area in FIG. 8), halftone display based on area gray scale is enabled for each display pixel.

Incidentally, in the example shown in FIG.
7 and the X-direction electrode 28 have the same density. That is, in the liquid crystal display device shown in FIG. 1, as described with reference to FIG. 5, the potential of the ferroelectric layer 26 decreases at a position apart from each of the Y-direction electrode 27 and the X-direction electrode 28 by a predetermined distance. As a result, there was a region where polarization did not occur, but the ferroelectric layer 2
6 and the mesh-shaped electrode, the electric potential in the region divided by the Y-direction electrode 27 and the X-direction electrode 28 is substantially uniform, and the ferroelectric layer 26 is formed in the entire region. Has an electric field (potential difference) higher than the coercive electric field required for polarization reversal.

[0063]

As described above, the active matrix display device of the present invention has a ferroelectric layer between a pixel electrode and a counter electrode, and the ferroelectric layer is provided between the pixel electrode and the counter electrode. The image information can be stored by the electric field exceeding the coercive electric field of the polarization reversal by the mesh-shaped electrode located at the position (1). That is, when the screen is not rewritten, only the power that can maintain the potential difference required to maintain the polarization of the ferroelectric layer is consumed, and the screen can be displayed. Therefore, a display device which consumes less power and has a power supply capacity that can display a screen for at least a long time is provided.

According to the liquid crystal display of the present invention,
By changing a plurality of regions in one pixel divided by the mesh-shaped electrode arbitrarily from transmission to absorption or absorption to transmission separately from the driving of one pixel unit by the TFT,
It is possible to display a gray scale by the area gray scale.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a first embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a schematic plan view of the liquid crystal display device shown in FIG.

FIG. 3 is a timing chart showing an example of a driving voltage applied to a mesh electrode of the liquid crystal display device shown in FIG.

4 is a graph showing an electric field (potential) applied to a ferroelectric layer by a mesh electrode of the liquid crystal display device shown in FIG.

FIG. 5 is a schematic diagram showing a state of a density change provided by a mesh electrode of the liquid crystal display device shown in FIG.

FIG. 6 is a sectional view schematically showing another embodiment of the liquid crystal display device shown in FIG. 1;

7 is a graph showing an electric field (potential) applied to a ferroelectric layer by a mesh electrode of the liquid crystal display device shown in FIG.

8 is a schematic diagram showing a state of a density change provided by a mesh electrode of the liquid crystal display device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 10 ... Array substrate, 13 ... Scan line (gate electrode), 14 ... Gate insulating film, 15 ... A-Si layer, 16 ... Inorganic protective film, 17 ... Omic contact layer, 18 ... ITO film ( Pixel electrode), 19: signal line (column selection line), 21: electrode portion (source), 22: electrode portion (drain), 23: TFT, 26: ferroelectric layer, 27: Y-direction electrode (mesh-shaped column) 28) X-direction electrode (mesh-shaped row electrode), 40: counter substrate, 45: counter electrode, 50: liquid crystal layer, 100: liquid crystal display device, 110: array substrate, 126: semiconductor layer.

Claims (15)

[Claims] 1. A ferroelectric layer disposed in contact with a first electrode disposed on one surface of a liquid crystal layer and having a dielectric constant of 10 or more and less than 5000, and a state in which the liquid crystal layer is interposed. A second electrode opposed to the first electrode and disposed facing the liquid crystal layer, and a third electrode disposed between the liquid crystal layer and the ferroelectric layer. A matrix type display device comprising: 2. The method according to claim 1, wherein the third electrode has a first direction and a first direction.
The matrix-type display device according to claim 1, wherein the display device is a mesh-like electrode including a plurality of electrodes each extending in a second direction substantially orthogonal to the direction. 3. The matrix type display device according to claim 2, wherein a semiconductor layer is disposed between said ferroelectric layer and said third electrode. 4. The liquid crystal device according to claim 1, wherein the third electrode is arranged so as to divide a region corresponding to one pixel of the liquid crystal layer divided by the first electrode into a plurality of regions that can be driven independently. The matrix type display device according to claim 1, wherein 5. The method according to claim 1, wherein the third electrode has a first direction and a first direction.
The matrix type display device according to claim 4, wherein the matrix type display device is a mesh electrode including a plurality of electrodes each extending in a second direction substantially orthogonal to the direction. 6. The matrix type display device according to claim 5, wherein a semiconductor layer is disposed between said ferroelectric layer and said third electrode. 7. The liquid crystal device according to claim 1, wherein the third electrode provides an area corresponding to one pixel of the liquid crystal layer by at least two or more areas divided by the third electrode. Matrix type display device. 8. The first electrode according to claim 1, wherein said third electrode has a first direction and a first direction.
The matrix-type display device according to claim 7, wherein the display device is a mesh-like electrode including a plurality of electrodes each extending in a second direction substantially orthogonal to the direction. 9. The matrix type display device according to claim 8, wherein a semiconductor layer is disposed between said ferroelectric layer and said third electrode. 10. The matrix type display device according to claim 1, wherein said first electrode is a reflection electrode defining a region corresponding to one pixel of said liquid crystal layer. 11. The method according to claim 11, wherein the third electrode is a mesh electrode including a plurality of electrodes extending in a first direction and a second direction substantially orthogonal to the first direction. A matrix type display device according to claim 10. 12. The method according to claim 12, wherein said ferroelectric layer and said third electrode are
12. The semiconductor device according to claim 11, wherein a semiconductor layer is provided.
5. A matrix type display device according to item 1. 13. The matrix type display device according to claim 1, wherein the third electrode is capable of dividing a region corresponding to one pixel of the liquid crystal layer into a plurality of regions having different transmittances. . 14. The method according to claim 14, wherein the third electrode is a mesh electrode including a plurality of electrodes extending in a first direction and a second direction substantially orthogonal to the first direction. A matrix type display device according to claim 13. 15. The method according to claim 15, wherein the ferroelectric layer and the third electrode are
15. The semiconductor device according to claim 14, wherein a semiconductor layer is disposed.
5. A matrix type display device according to item 1.